5. Primary dentin the most prominent dentin in the tooth, lies between the enamel and the pulp chamber. Secondary dentin is formed after root formation is complete, normally after the tooth has erupted and is functional. It grows much slower than primary dentin.The growth of this type of dentin causes the decrease in the size of the pulp chamber with age; this is why cavity preparation in young patients is risky which may lead to exposing the pulp.
9. peritubular / intratubular dentine dentin that forms the wall of each tubule more mineral than intertubular dentin intertubular dentine dentine between the tubules
21. Hydrodynamic theory : Fluid movements in the dentinal tubules – the tubular nature of dentin permits fluid movement to occur within the tubule when a stimulus is applied – a movement registered by pulpal free nerve endings close to the dentin. Brannstrom’s Theory.